Monday, January 30, 2012

1201.5576 (E. V. Gorelik et al.)

Universal probes for antiferromagnetic correlations and entropy in cold
fermions on optical lattices

E. V. Gorelik, D. Rost, T. Paiva, R. Scalettar, A. Klümper, N. Blümer
We determine antiferromagnetic (AF) signatures in the half-filled Hubbard
model at strong coupling for a cubic lattice and in lower dimensions. Upon
cooling, the transition from the charge-excitation regime to the AF Heisenberg
regime is signaled by a universal minimum of the double occupancy at entropy
S/(N k_B)=log(2) per particle and a linear increase of the next-nearest
neighbor (NNN) spin correlation function below. This crossover, driven by a
gain in kinetic exchange energy, appears as the essential AF physics relevant
for current cold-atom experiments. The detection of long-range AF order
requires measurements of spin correlations at or beyond NNN distances.
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